In the case where a combustible fluid (electrically insulating fluid) such as an organic solvent flows through an insulating resin-made tube, conventionally, the tube is easily electrically charged by friction with the combustible fluid. Also in the case where, in a factory or the like in which an insulating resin-made tube is used, the insulating resin-made tube is rubbed with a clean room glove, the tube is easily electrically charged.
As means for preventing an insulating resin-made tube from being electrically charged, therefore, countermeasures have been taken in which an electrically conductive material (hereinafter, referred to simply as “conductive material”) such as graphite or fine metal powder is disposed in the insulating resin-made tube in order to make the tube electrically conductive. In a fluororesin-made tube (insulating resin-made tube) disclosed in Patent Literature 1, for example, conductive portions containing a conductive material are disposed in the outer circumferential surface of the tube body which is configured by a transparent portion in order to ensure the visibility.
In the fluororesin-made tube disclosed in Patent Literature 1, however, the conductive portions are elongated in a stripe manner along the longitudinal direction of the tube body. Depending on the installation situation, therefore, the conductive portions cannot be positioned in a required place of the tube in the case where a combustible fluid flows at a low rate, and there is a possibility that the function of preventing the tube from being electrically charged cannot be sufficiently exerted.
Moreover, the technique disclosed in Patent Literature 1 uses the configuration where the tube contains a conductive material, i.e., that where the tube itself is caused to have electrically conductive property. Therefore, the technique cannot be applied to an existing tube made of only fluororesin (insulating resin), and consequently the existing tube cannot be provided with the electrical charge preventing function.